package com.zdp.io.nio.test1;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Date;
import java.util.Iterator;
import java.util.Set;

/**
 * @author ZhengDp
 * @Date 2024/2/26 23:35
 */
public class MultiplexerTimeServer implements Runnable{

    private Selector selector;

    private volatile boolean stop;

    /**
     * 服务端通道
     */
    private ServerSocketChannel serverSocketChannel;

    public MultiplexerTimeServer(int port) {
        try {
            selector = Selector.open();
            serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.socket().bind(new InetSocketAddress(port), 1024);
            // selector 监听 channel 上的 ACCEPT事件
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
            System.out.println("The time server is start in port : " + port);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    public void stop() {
        this.stop = true;
    }

    /**
     * 轮询 就绪事件， 将客户端的Socket注册到Selector上，并监听对应的事件
     */
    @Override
    public void run() {
        while(!stop) {
            try {
                selector.select(1000);
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = selectionKeys.iterator();
                SelectionKey key = null;
                while(iterator.hasNext()) {
                    key = iterator.next();
                    // 事件处理完毕后需要移除，否则会重复处理
                    iterator.remove();
                    try {
                        handleInput(key);
                    } catch (Exception e) {
                        if (key != null) {
                            key.cancel();
                            if (key.channel() != null) {
                                key.channel().close();
                            }
                        }
                    }

                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }

    private void handleInput(SelectionKey key ) throws IOException{
        if(key.isValid()) {
            // 处理 ACCEPT 事件
            if(key.isAcceptable()) {
                ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
                SocketChannel sc = ssc.accept();
                sc.configureBlocking(false);
                sc.register(selector,SelectionKey.OP_READ);
            }
            // 处理 READ 事件
            if(key.isReadable()) {
                SocketChannel sc = (SocketChannel) key.channel();
                ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                int readBytes = sc.read(readBuffer);
                if (readBytes > 0) {
                    // 写转读
                    readBuffer.flip();
                    byte[] bytes = new byte[readBuffer.remaining()];
                    readBuffer.get(bytes);
                    String body = new String(bytes,"UTF-8");
                    System.out.println("The time server receive order : " + body);
                    String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ?
                            new Date(System.currentTimeMillis()).toString() : "BAD ORDER";
                    doWrite(sc,currentTime);
                } else if(readBytes < 0) {
                    // 对端链路关闭
                    key.cancel();
                    sc.close();
                } else {
                    ; // 读到0字节，忽略（正常场景）
                }
            }
        }
    }

    private void doWrite(SocketChannel channel, String response) throws  IOException{
        if(response != null && response.trim().length() > 0) {
            byte[] bytes = response.getBytes();
            ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
            writeBuffer.put(bytes);
            writeBuffer.flip();
            channel.write(writeBuffer);
        }
    }
}
